Cancer therapy comprising deaminase enzyme inhibitors

ABSTRACT

The present invention provides materials and methods for the treatment of neoplastic disease states, especially cancers of cells/organs of epithelial origin. For example, the invention provides chemotherapeutic materials and methods for treatment comprising an inhibitor of at least one of the enzymes adenosine deaminase and AMP deaminase.

FIELD OF THE INVENTION

[0001] The present invention relates generally to the field of medicine. More particularly, the invention relates to the field of oncology, especially the treatment of cancers of an epithelial origin.

DESCRIPTION OF RELATED ART

[0002] Purine nucleosides (e.g., adenosine, deoxyadenosine, guanosine, deoxyguanosine), which comprise bi-cyclic nitrogenous purine bases (adenine, guanine) linked to a pentose sugar (ribose, deoxyribose), are found in all cell types, e.g., serving as constituent nucleosides of both ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). At high concentrations, purines and their derivatives have been shown to arrest normal cell growth and cause apoptosis in certain cell types, such as endothelial cells, macrophages, and lymphocytes. It has been hypothesized that cell death usually occurs through conversion of adenosine into nucleotides (via phosphorylation) and/or into S-adenosylhomocysteine, which in turn induce pyrimidine starvation or inhibit cellular methylation. The high concentrations of adenosine necessary to cause cell death are difficult to maintain, however, due to the many cellular processes by which adenosine can be converted to other products. See Bynum, Cancer Res. 40: 2147-2152 (1980); Archer et al., J. Cell. Phys. 124:226-232 (1985); Henderson et al., Pharmac. & Ther. 8: 539-571 and 573-604 (1980).

[0003] Blay et al. Cancer Research 57: 2602-2605 (1997); Hoskin et al. Int. J. Cancer 59: 854-855 (1994), Williams et al. Biochemical and Biophysical Research Communications 231: 264-269 (1997), and MacKenzie et al. Experimental Cell Research 276: 90-11 (2002) observed elevated levels of extracellular adenosine associated with certain tumors and that administration of coformycin further increased local adenosine concentrations. The authors concluded that the high extracellular adenosine levels suppress the local antitumor immune response of T-killer cells, inactivating their anti-tumor function and contributing to overall tumor survival.

[0004] Adenosine (Ado) is reportedly released from cells in response to alterations in oxygen supply or demand, and has been reported to be a potent vasodilator involved in the metabolic regulation of blood flow. At less than toxic concentrations, adenosine has been reported to have both cardio-protective and neuro-protective properties [Olafsson et al., Circulation, 76: 1135-1145 (1987); Dragunow and Faull, Trends in Pharmacol. Sci., 9:193 (1988).]

[0005] Adenosine deaminase (ADA) is the hydrolytic enzyme that catalyzes the deamination of adenosine and deoxyadenosine to inosine and deoxyinosine, and thus is one of the enzymes involved in controlling adenosine/deoxyadenosine levels. ADA is found at especially high levels in the spleen, thymus, and B and T lymphocytes. Adenosine monophosphate deaminase (AMP deaminase, AMPDA) is functionally related to adenosine deaminase, converting adenosine monophosphate to inosine monophosphate. ADA plays an essential role in leukocytes and its absence is associated with a severe, inherited combined immunodeficiency disease.

[0006] Interestingly, although ADA is capable of deaminating both adenosine and 2-deoxyodenosine (dAdo), it is principally dAdo that accumulates in plasma following dosing with an ADA inhibitor, such as deoxycoformycin (dCF). Apparently, deamination of adenosine occurs principally at the monophosphate level by the enzyme AMP deaminase. The dAMP moiety is a poor substrate for AMP deaminase, so deamination of dAdo is largely dependent on ADA, and ADA-inhibition results in dAdo accumulation. [Plunkett and Gandhi, Hematol. Cell Ther. 38: S67-S74 (1996).]

[0007] Inhibitors of ADA have been recognized as potential immunosuppressive agents, and many early studies of the cytotoxicity of adenosine deaminase inhibitors have involved human lymphocytes. [See, e.g., O'Dwyer et al., Annals Int. Med. 108: 733-743 (1988).] For example, dCF, a powerful ADA inhibitor (K, for erythrocyte ADA of 2×10⁻¹²), has been used to treat lymphatic leukemias and is FDA-approved (Pentostatin) to treat hairy cell leukemia. Coformycin, the ribosyl analog of dCF, also acts as an ADA inhibitor. The pharmacology and efficacy of dCF and two other prominent nucleoside analogs—2-chlorodeoxyadenosine, (CDA, cladribine) and arabinosyl-2-fluoroadenine monophosphate (F-ara-AMP, fludarabine)—for treating lymphoid malignancies are reviewed in Plunkett and Gandhi, Hematol. Cell Ther. 38: S67-S74 (1996), and Dillman, R., Seminars in Hematoloogy, 31: 16-27 (1994), incorporated herein by reference. The toxicity of ADA inhibitor compounds appears to relate to their causing an accumulation of toxic intracellular levels of dAdo, which (through conversion to dATP via successive phosphorylations) inhibits ribonucleotide reductase. The lethal effects of dAdo on blood cells has been extensively studied and reported in the literature.

[0008] Not all of the studies involving ADA inhibitors have focused on lymphoid malignancies. Camici et al., Int. J. Cancer, 62: 176-183 (1995) reported an assessment of the effect of deoxycoformycin (0.001 to 1 μM) and 2′-deoxyadenosine (0 to 500 μM) on the growth of two cultured human colon carcinoma cell lines and on Chinese hamster ovary (CHO K-I) cells. Neither compound was reported to be toxic when used alone, whereas their combination was reported to cause cell growth inhibition, with the CHO cells more sensitive than the colon carcinoma cells. At the concentrations tested, 50-150 pM deoxyadenosine was required to approach full cell growth inhibition. The authors suggest that phosphorylation of deoxyadenosine by adenosine kinase plays a central role in the toxicity of the combination therapy, and observed that the cytotoxic effect was almost completely reversed in the three cell lines when inhibitors of adenosine kinase were added to the cell culture medium. Introduction of dipyridamole to inhibit deoxyadenosine uptake also was reported to reverse the toxicity.

[0009] Svendsen et al., Cancer Chemotherapy & Pharmacology 21(1): 35-39 (1988) reported that simultaneous administration of 3′deoxadenosine N1-oxide and either EHNA or dCF to mice bearing Ehrlich ascites tumor cells resistant to 3′-deoxyadenosine N1-oxide resulted in 80-90% inhibition of tumor growth in vivo.

[0010] Rowland et al., Arch. Biochem. Biophys., 239(2): 396-403 (1985) developed a rat hepatoma cell line that was ADA-dependent and dCF sensitive. The authors observed that dCF-resistant variants developed and determined that such cells have progressively increasing concentrations of ADA activity, apparently resulting from ADA gene amplification. A dCF-resistant CHO cell line developed by the authors also demonstrated extreme increases in ADA activity, but this change was not attributable to gene amplification.

[0011] Wakade et al., J. Biol. Chem., 270(30): 17986-17992 (1995) have shown that dAdo (which increases in concentration in the presence of an ADA inhibitor) causes neuronal cell toxicity in a dose-dependent manner (maximal at 300 μM). Neuronal death was correlated to a dramatic increase in the dATP content of the neurons. Nanomolar concentrations of 5′-Iodotubercidin (ITu) were reported to completely and dose-dependently inhibit formation of dATP and protect against toxicity of sub-millimolar concentrations of dAdo. Interestingly, neither dCF nor another ADA inhibitor [erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA)] at concentrations of 3-30 μM were found to modify the toxic effects of dAdo in the neuronal model. [See also Kulkami and Wakade, J. Neurochem., 67(2): 778-786 (1996).] Wakade et al., J. Neurochemistry 67(6):2273-2281 (December, 1996) reported that 100 μM dAdo (but not adenosine) in combination with 3 μM dCF was toxic to chromaffin cells. The toxicity, which was associated with dATP accumulation, was eliminated by co-culture with nanomolar concentrations of ITu.

[0012] There also exists suggestions in the literature for using AMP deaminase inhibitors for therapeutic purposes. For example, Gruber and colleagues have suggested using AMP deaminase inhibitors to treat or prevent a variety of cardiovascular and other disorders. [See U.S. Pat. Nos. 5,731,432 and 4,912,092.]

[0013] The treatment of parasitic (e.g., fungal, trypanosomal) infections with ADA inhibitors in combination with 3′-deoxypurine nucleosides (e.g., cordycepin) has been suggested. See McCaffrey et al., U.S. Pat. Nos. 5,679,648 and 5,663,155 and International Patent Publication No. WO 96/16664.

[0014] Extracellular adenosine and adenosine triphosphate (ATP) have also been reported to cause cytotoxicity. For example, Dawicki et al., Am. J. Physiol., 273: L485-L494 (1997) reviewed literature reporting ATP-induced apoptosis in lymphocytes, and reported that extracellular ATP, ADP, AMP, adenosine, and non-metabolized adenosine analogs [3-deaxaadenosine and Z-5′-fluoro-4′,5′-didehydro-5-deoxyadenosine (MDL-28842)] caused apoptosis of pulmonary artery endothelial cells. The authors concluded that the ATP metabolite adenosine was responsible for the observed toxicity, since adenosine itself and nucleotides that are degraded to adenosine caused DNA damage, whereas non-metabolizable ATP analogs (e.g., ATPγS) and several adenosine metabolites did not. The extracellular ATP-induced cleavage (observed at 10 μM ATP, statistically significant at 100 μM) was reportedly prevented by the nucleoside transport inhibitor dipyridamole.

[0015] Bynum, J. W., Cancer Res., 40: 2147-2152 (July, 1980) reported that mouse melanoma cells were “moderately sensitive” to adenosine, with 80% growth inhibition being observed at 50 μM, compared to 5 μM or 400 μM reportedly required to achieve similar effects in lymphoid cells and fibroblasts, respectively. The different sensitivities were not attributed to ADA, because the lymphoid cells had two to four times the level of ADA activity than the melanoma cells or fibroblasts. The authors suggested that adenosine's toxicity may be caused by interruption of pyrimidine biosynthesis and resultant depletion of pyrimidines. Guanosine also reportedly possessed growth-inhibitory properties. The author reported that homocysteine thiolactone (HCT) enhanced the cytotoxicity of adenosine, but not of guanosine. See also Archer et al., J. Cell. Physiol., 124: 226-232 (1985).

[0016] Homocysteine is a compound which, in high concentrations, has been identified as a prevalent risk factor for myocardial infarction and stroke. Wang et al., J. Biol. Chem., 272(40): 25380-85 (October, 1997) reported that homocysteine (10-50 μM, a range that overlaps levels observed clinically) caused inhibition of DNA synthesis in vascular endothelial cells and arrested their growth at the G₁ phase of the cell cycle, which may play an important role in the arteriosclerotic disease process. Kredich et al., Proc. Natl. Acad. Sci. USA, 76(5): 2450-2454 (1979) reported that addition of 100 μM L-homocysteine thiolactone to cells treated with the ADA inhibitor EHNA and adenosine had the effect of enhancing adenosine toxicity towards a human lymphoblast cell line.

[0017] Yet another body of research has focused on use of purine nucleotides or hydrolysis-resistant purine nucleotide analogs as anti-neoplastic agents. For example, Trepel et al., U.S. Pat. Nos. 5,415,873 and 5,641,500, report that certain hormone-independent prostatic tumor cell lines express a P₂ subtype purinergic receptor which interact with ATP, and that such growth of such cell lines is inhibited by ATP. Adenosine, which lacks phosphate moieties, is reported to be from about 40-fold to about 500-fold less potent an agonist than ATP of these cell types.

[0018] In U.S. Pat. No. 5,227,371, Rapaport reports that adenine nucleotide or adenosine plus inorganic phosphate, but not adenosine alone, yields a sustained “secondary wave” of extracellular blood plasma ATP levels. Rapaport suggests that extracellular ATP increases may have several beneficial effects, including tumor growth inhibition. In U.S. Pat. Nos. 5,049,372 and 4,880,918, Rapaport suggests that ATP or ADP can be used as selective tumor growth inhibition agents, whereas purines will inhibit the growth not only of tumor cells but also of normal cells. Rapaport's explanation is that ADP or ATP penetrate the plasma membrane of tumor cells, but not normal cells, without degradation to AMP or adenosine. Rapaport explicitly states that the observed effects on cellular growth is unique to ADP and ATP and cannot be duplicated by adenosine.

[0019] Thus, purine nucleosides, purine nucleotides, derivatives thereof, and ADA inhibitors have been investigated by several research groups and, in some instances such as the treatment of hairy cell leukemia with dCF, have shown limited success. However, neoplastic diseases (e.g., cancer) remain one of the leading killers in modern societies, and a long felt need exists for new therapeutic regimens to treat neoplastic diseases, especially non-lymphoid related neoplastic diseases. A long felt need also exists for effective treatments which can be carefully controlled and modulated to maintain efficacy and minimize toxicity to the patient's non-cancerous tissues and cells.

SUMMARY OF THE INVENTION

[0020] The present invention provides novel chemotherapeutic materials and methods that address one or more of the foregoing long felt needs.

[0021] In particular, the present invention provides materials and methods for the treatment of neoplastic disease states, especially cancers of cells/organs of epithelial origin. For example, the invention provides combination chemotherapy materials and methods for treatment comprising a first agent comprising adenosine or an adenosine derivative and a second agent comprising an inhibitor of at least one of the enzymes adenosine deaminase and AMP deaminase.

[0022] In one embodiment, the invention provides a composition comprising: a first compound selected from the group consisting of adenosine, adenosine derivatives, and pharmaceutically acceptable salts thereof, in admixture with a second compound selected from the group consisting of adenosine deaminase inhibitors (ADAI), adenosine monophosphate deaminase inhibitors (AMPDAI), and pharmaceutically acceptable salts thereof. Since the composition is useful for medical treatment, in a preferred embodiment it also comprises a pharmaceutically acceptable carrier. The composition may further include additional therapeutic agents, such as homocysteine compounds that potentiate the effects of the first two compounds, and/or additional agents such as preservatives and the like. ADAI and AMPDAI compounds whose inhibitory activities are characterized by sub-nanomolar inhibition constants (K_(1≦)1 nM) are preferred. In one preferred variation, the second compound of the composition has dual activities as both an ADAI and an AMPDAI. In another variation, the second compound is an ADAI, and the composition further includes a third compound that is an AMPDAI.

[0023] In a related embodiment, the invention provides a unit dose comprising: a first composition comprising a member selected from the group consisting of adenosine, adenosine derivatives, and pharmaceutically acceptable salts thereof; and a second composition comprising a member selected from the group consisting of adenosine deaminase inhibitors, adenosine monophosphate deaminase inhibitors, and pharmaceutically acceptable salts thereof. The compositions are preferably included in the unit dose at concentrations effective to inhibit the growth of neoplastic cells in a cancer patient. Concentrations effective to maintain a peritoneal concentration of the compound or compounds of at least 5 μM for at least 12 hours is typically sufficient.

[0024] In one variation, the unit dose is formulated wherein the first and second compositions are in admixture with each other. Preferably this mixture further includes a pharmaceutically acceptable carrier. In yet another variation, the unit dose is formulated such that the first and second compositions are packaged together as a kit, but are not in admixture. Separate packaging of the two compositions permits administration by separate routes, at separate times, and/or at separate rates, and permits formulating each composition uniquely.

[0025] In a preferred embodiment, the unit dose is packaged as kit with one or more additional compositions that are useful for enhancing the treatment regimen of a cancer patient. For example, the unit dose further includes a composition that comprises homocysteine in an amount effective to potentiate the anti-neoplastic activity of the first and second compositions.

[0026] In a highly preferred embodiment, the unit dose further includes a composition that comprises a protective agent such as a nucleoside transport inhibitors or adenosine kinase inhibitor. It is contemplated that the two or more anti-neoplastic therapeutic agents are administered via a route designed to achieve high concentrations at the site of a tumor, whereas the protective agent(s) is administered systemically to protect healthy (non-cancerous) tissues from the anti-neoplastic agents. Such kits for treating a neoplastic disease state may further comprise a label attached to or packaged with the containers of the kit, the label describing uses of the compounds for treatment of a neoplastic disease state.

[0027] The invention also provides for methods of treatment that involve administration of compounds, compositions, and unit doses of the invention for the treatment of disease states, particularly neoplastic disease states. For example, the invention provides a method of treating a neoplastic disease state in a patient in need of such treatment, comprising the steps of: administering to a patient suffering from a neoplastic disease state a first compound selected from the group consisting of adenosine, adenosine derivatives, and pharmaceutically acceptable salts thereof, and a second compound selected from the group consisting of adenosine deaminase inhibitors (ADAI), adenosine monophosphate deaminase inhibitors (AMPDAI), and pharmaceutically acceptable salts thereof.

[0028] As explained below, treatment of malignancies of epithelial cell origin, such as those of the lungs, breasts, gastrointestinal system, genitorurinary tract, or reproductive organs is specifically contemplated. A highly preferred embodiment involves treatment of ovarian cancers.

[0029] In one variation, the method of treatment involves administering one or more of the anti-neoplastic compounds in a manner that generates high concentrations in or around the tumor area, and administering protective agents systemically to protect the patient's healthy tissues and cells, including the heart, against toxic side-effects of the anti-neoplastic compounds.

[0030] Elevated adenosine has been observed in tumors and/or the extracellular fluid of certain tumors, and for such tumors, the invention provides a method of treatment comprising administering to a mammalian subject a composition comprising a compound selected from the group consisting of adenosine deaminase inhibitors (ADAI), adenosine monophosphate deaminase inhibitors (AMPDAI), and pharmaceutically acceptable salts thereof. One anti-neoplastic compound (e.g., the ADAI or AMPDAI) is effective in these circumstances, without the necessity of also administering adenosine or adenosine derivatives in combination.

[0031] In a related embodiment, the invention provides a method of treatment comprising steps of screening a mammalian subject for a tumor and for elevated adenosine in the tumor or in extracellular fluid of the tumor, and administering to a mammalian subject diagnosed with the tumor and the elevated adenosine a composition comprising a compound selected from the group consisting of adenosine deaminase inhibitors (ADAI), adenosine monophosphate deaminase inhibitors (AMPDAI), and pharmaceutically acceptable salts thereof.

[0032] Mammalian subjects other than rodents are preferred. Primates are highly preferred. Human subjects are very highly preferred. Coformycin is a preferred compound. The ADAI or AMPDAI is preferably administered at a dose that is toxic (growth-arresting or killing) to the tumor having the elevated adenosine concentration, yet nontoxic to healthy cells with normal adenosine concentrations in the cells or extracellular environment, thereby reducing deleterious side effects.

[0033] In still another embodiment, the invention provides a kit comprising a container containing a compound selected from the group consisting of adenosine deaminase inhibitors (ADAI), adenosine monophosphate deaminase inhibitors (AMPDAI), and pharmaceutically acceptable salts thereof, and a label affixed to or packaged with the container, the label containing instructions for administering the compound to a patient having a solid tumor. In one variation, the compound is present in the kit as part of a composition, e.g., including an appropriate carrier as described in greater detail below.

[0034] In still another embodiment, the invention provides the use of a compound in the manufacture of a medicament for the treatment of solid tumors, wherein the compound is selected from the group consisting of adenosine deaminase inhibitors (ADAI), adenosine monophosphate deaminase inhibitors (AMPDAI), and pharmaceutically acceptable salts thereof. In particular, the compound is used for the manufacture of a medicament for the treatment of solid tumors having elevated adenosine in the tumor or in extracellular fluid of the tumor.

[0035] Additional features and variations of the invention will be apparent to those skilled in the art from the entirety of this application, including the drawing and detailed description, and all such features are intended as aspects of the invention. Likewise, features of the invention described herein can be re-combined into additional embodiments that also are intended as aspects of the invention, irrespective of whether the combination of features is specifically mentioned above as an aspect or embodiment of the invention. Also, only such limitations which are described herein as critical to the invention should be viewed as such; variations of the invention lacking limitations which have not been described herein as critical are intended as aspects of the invention.

[0036] In addition to the foregoing, the invention includes, as an additional aspect, all embodiments of the invention narrower in scope in any way than the variations specifically mentioned herein. Although the applicant(s) invented the full scope of the claims appended hereto, the claims appended hereto are not intended to encompass within their scope the prior art work of others. Therefore, in the event that statutory prior art within the scope of a claim is brought to the attention of the applicants by a Patent Office or other entity or individual, the applicant(s) reserve the right to exercise amendment rights under applicable patent laws to redefine the subject matter of such a claim to specifically exclude such statutory prior art or obvious variations of statutory prior art from the scope of such a claim. Variations of the invention defined by such amended claims also are intended as aspects of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037]FIG. 1 is a bar graph depicting the efficacy of adenosine, coformycin, and the combination thereof for killing breast cancer (MCF7) and ovarian cancer (OVCAR3) cell lines. The results are presented as the percent of viable (surviving) cells (compared to an untreated control) following a sixty hour treatment regimen.

[0038]FIG. 2 is a bar graph depicting the efficacy of 10 μM adenosine combined with 10 μM coformycin for killing several tumor cell lines: MCF7 and MDA MB 231 breast cancer cell lines; OVCAR 3 and OVCAR 5 ovarian cancer cell lines; HT 29 colon cancer cell line; and PC3, TSU-Pr1, and DU14 prostatic cancer cell lines. The results are presented as the percent of surviving cells (compared to an untreated control) following a sixty hour exposure to the drug combination.

[0039]FIG. 3 is a bar graph depicting the efficacy of adenosine in combination with coformycin for killing cells of an ovarian cancer (OVCAR3) cell line, and the ability of the nucleoside transport inhibitor dipyridamole to protect the cells from the cytotoxic effects of this drug combination. The results are presented as the percent of viable (surviving) cells (compared to an untreated control) following a sixty hour treatment regimen.

[0040]FIG. 4 is a bar graph depicting the efficacy of adenosine in combination with coformycin for killing cells of an ovarian cancer (OVCAR3) cell line, and the ability of the adenosine kinase inhibitor 5′-amino-5′-deoxyadenosine to protect the cells from the cytotoxic effects of this drug combination. The results are presented as the percent of viable (surviving) cells (compared to an untreated control) following a sixty hour treatment regimen.

[0041]FIG. 5 is a bar graph depicting the efficacy of adenosine in combination with coformycin for killing cells of several cancer cell lines (OVCAR3, OVACAR5, DU145, PC3, LNCaP, TSU-PR1, and MCF-7), and the ability of the nucleoside transport inhibitor dipyridamole to protect the cells from the cytotoxic effects of this drug combination. The results are presented as the percent of viable (surviving) cells (compared to an untreated control) following a sixty hour treatment regimen. Error bars depict standard deviation (representative of three different analyses).

[0042]FIG. 6 is a bar graph depicting the efficacy of adenosine in combination with either coformycin or deoxycoformycin for killing cells of several cancer cell lines (OVCAR3, OVACAR5, MCF-7, HT29). The results are presented as the percent of viable (surviving) cells (compared to an untreated control) following a sixty hour treatment regimen.

[0043]FIG. 7 is a bar graph depicting the efficacy of adenosine in combination with coformycin and coformycin alone for killing cells from solid tumors, explants derived from mice subcutaneously implanted with two ovarian cancer cell lines, OVCAR3 and OVCAR5. The results are presented as the percent of viable (surviving) tumor cells compared with an untreated control following a ninety-six hour treatment regimen.

DETAILED DESCRIPTION OF THE INVENTION

[0044] The invention provides a composition comprising: a first compound selected from the group consisting of adenosine, adenosine derivatives, and pharmaceutically acceptable salts thereof, in admixture with a second compound selected from the group consisting of adenosine deaminase inhibitors (ADAI), adenosine monophosphate deaminase inhibitors (AMPDAI), and pharmaceutically acceptable salts thereof. As described herein in detail, such compositions are considered useful for the treatment of neoplastic diseases. Therefore, the composition preferably contains the compounds at a therapeutically effective molar ratio. In a preferred embodiment, the molar ratio of the two compounds is 0.01 to 100; in a highly preferred embodiment 0.1 to 10; and in a very highly preferred embodiment, about 1.0.

[0045] Adenosine, as explained above, is a naturally occurring nucleoside comprised of the purine adenine linked to ribose, and is involved in numerous vital biological processes in all organisms, including metabolic processes and synthesis of nucleic acids. Adenosine is commercially available from numerous commercial suppliers and is FDA-approved for use in human patients.

[0046] The term “adenosine derivative” is intended to encompass:

[0047] (1) compounds comprising a pentose ring (including but not limited to ribose and deoxyribose) coupled to a purine (e.g., adenine, guanine) base;

[0048] (2) compounds as set forth in (1) which further include additions, deletions, and/or substitutions at the 2′ or 3′ positions of the ribose ring or at any site on the adenine rings. Additions or substitutions with chemical moieties including hydrogen, hydroxyl, halogens, C₁-C₆ alkyls and alkoxyls, amines, amides, sulfhydrals, sulfinyls, sulfonyls, nitryls, phosphoryls, and combinations of the foregoing are contemplated. Compounds having one, two, three, four, or five, or six such substitutions are explicitly contemplated. Cordycepin (3′-deoxyadenosine) and cordycepin derivatives are specifically contemplated; and

[0049] (3) “pro-drugs” that, when administered to patients, are metabolized or altered in vivo into adenosine or adenosine derivatives as set forth in (1) or (2). For example, mono- di- and tri-phosphate nucleotides of adenosine or adenosine derivatives are contemplated.

[0050] Compositions of the invention that [preferably] contain adenosine or an adenosine derivative preferably do so at a concentration of between about 1.0 nM to 100 mM; and more preferably 100 nM to 10 mM; and still more preferably 10 μM to 10 mM. Higher concentration compositions may be preferred for shipping and/or storage and may be diluted with pharmaceutically acceptable diluents, adjuvants, excipients, carriers, or the like prior to administration to patients.

[0051] The adenosine deaminase inhibitors or adenosine monophosphate deaminase inhibitors may be any compound that prevents adenosine deaminase and/or adenylate (AMP) deaminase enzymes from deaminating their respective substrates. Inhibitors that demonstrate specificity for such deaminase enzymes and that do not interfere with unrelated cellular processes are preferred. As set forth below, inhibitors such as coformycin that exhibit greater inhibitory activity toward AMPDA are highly preferred. The terms “adenosine deaminase inhibitor” and “AMP deaminase inhibitor” are also intended to include “pro-drugs” that, when administered to patients, are metabolized or altered in vivo into compounds that act as ADAI's or AMPDAI's.

[0052] The literature contains numerous descriptions of deaminase inhibitors that are suitable for use in the present invention. For example, the production of the ADAI/AMPDAI coformycin is described in Umezawa et al., U.S. Pat. Nos. 4,014,769 and 3,959,257; Umezawa et al., U.S. Pat. No. 4,163,839 and Shimazaki et al., J. Antibiot. (Tokyo), 32:537 (1979) describe the ADA inhibitor isocoformycin (a structural isomer of coformycin); Erion et al., U.S. Pat. No. 5,731,432, International Patent Publication No. WO 94/18200, and Gruber U.S. Pat. No. 4,912,092 describe AMPDA inhibitors; Schaeffer et al., U.S. Pat. No. 4,315,920, describes adenosine deaminase inhibitors that are derivatives of 9-alkyladenines, such as 9-(2-hydroxy-3-alkyl)adenines, e.g., EHNA; Takeuchi et al., U.S. Pat. Nos. 5,886,167 and 5,773,607 describe 2′-fluoro derivatives of coformycin with high ADA-inhibitory activity; Yamada, U.S. Pat. Nos. 5,773,603 and 5,705,491 describes ADA inhibitors comprising an O-alkylated moiety. A process for large-scale isolation of 2′-deoxycoformycin is described in Showalter et al., J. Antibiotics, 45:1914-1918 (December, 1992). All of the foregoing documents are incorporated herein by reference in their entirety.

[0053] Since compositions of the invention are intended for administration to humans or animals for medical purposes, it will be appreciated that, in a preferred embodiment, compositions of the invention further comprise a pharmaceutically acceptable carrier. Such carriers may be any solid, liquid, or gaseous materials useful for the purpose of administering a medicament to a patient. Pharmaceutically acceptable carriers are preferably sterile, inert, non-toxic, and compatible with the active ingredients of the composition. Carriers include diluents or vehicles such as fillers, binding agents, disintegrators, and lubricants. Exemplary carriers include lactose, saccharose, sodium chloride, potassium phosphate, glucose, starch, calcium carbonate, crystal cellulose or silicic acid, water, ethanol, propanol, gelatins, caraboxylmethyl cellulose, methyl cellulose, sodium alginate, agar, sodium hydrogencarbonate, calcium carbonate, stearic acid monoglyceride, stearates, boric acid powders, solid polyethylene glycol, polyoxyethylene sorbit, solutions and suspensions of any of the foregoing, glycerine, oils, fatty acid esters, and the like. The compositions of the invention also may contain other active ingredients such as preservatives.

[0054] The compositions may take any conventional pharmaceutical form, including that of a solution, emulsion, suspension, ointment, cream, granule, powder, spray, tablet, capsule, lozenge, or suppository. One or more of the administered compounds may be encapsulated, e.g., in liposomes, to facilitate intracellular delivery.

[0055] It is further contemplated that compositions of the invention may be formulated to include additional agents that will enhance anti-neoplastic efficacy. For example, in a preferred embodiment, the composition further includes a homocysteine formulation, such as homocysteine thiolactone, at a concentration effective to enhance the toxicity of the composition towards tumors. For example, a molar ratio of adenosine: homocysteine of 0.01 to 1000 is contemplated, and a ratio of 1 to 100 is preferred. Moreover, the addition of other anti-neoplastic agents to the composition that improve therapeutic efficacy via a mechanism entirely independent of the first and second compounds is nonetheless considered within the scope of the invention. For compositions comprising a deaminase inhibitor alone, molar ratios of the deaminase inhibitor and the homocysteine of about 0.01 to about 1000 are contemplated. A molar ratio of about 1:100 is preferred.

[0056] In a related embodiment, the invention provides a unit dose comprising: a first composition comprising a member selected from the group consisting of adenosine, adenosine derivatives, and pharmaceutically acceptable salts thereof; and a second composition comprising a member selected from the group consisting of adenosine deaminase inhibitors, adenosine monophosphate deaminase inhibitors, and pharmaceutically acceptable salts thereof. In a preferred embodiment, the compositions are included in the unit dose at concentrations such that, when administered to a patient singly or repetitively, the unit dose will be effective to inhibit the growth of neoplastic cells in the patient. In preferred embodiments, the unit dose will be effective to kill the neoplastic cells. Concentrations effective to maintain a peritoneal concentration of the compound or compounds of at least 5 μM for at least 12 hours is typically sufficient.

[0057] In one variation, the unit dose is formulated wherein the first and second compositions are in admixture with each other. Preferably this mixture further includes a pharmaceutically acceptable carrier.

[0058] In yet another variation, the unit dose is formulated such that the first and second compositions are packaged together as a kit, but are not in admixture. A kit that includes each therapeutic agent packaged together in dosage form adds convenience to medical practitioners. Separate packaging of the two compositions permits administration by separate routes, at separate times, and/or at separate rates. Separate packaging also permits formulating each composition uniquely, e.g., with its own carriers and preservatives, to optimize shelf life and the like.

[0059] In a preferred embodiment (for both of the aforementioned variations), the unit dose of the invention is packaged as kit with one or more additional compositions that are useful for enhancing the treatment regimen of the patient. For example, the unit dose further includes a composition that comprises homocysteine in an amount effective to potentiate the anti-neoplastic activity of the first and second compositions.

[0060] In a highly preferred embodiment, the unit dose further includes a composition that comprises a protective agent to protect cells from the cytotoxic effects of the first and second compositions. In a preferred embodiment, the protective agent is selected from the group consisting of nucleoside transport inhibitors, adenosine kinase inhibitors, and pharmaceutically acceptable salts thereof Thus, in one treatment regimen of the invention, the one [two] or more anti-neoplastic therapeutic agents are administered via a route designed to achieve high concentrations at the site of a tumor, whereas the protective agent is administered systemically to protect healthy (non-cancerous) organs (e.g., heart), tissues, or cells (e.g., lymphoid cells) from the anti-neoplastic agents. For example, to treat non-metastasized ovarian cancer, the therapeutic agents are delivered intraperitoneally, e.g., via a series of injections or via a drug delivery pump. The protective agents is delivered intra-arterially or intravenously.

[0061] Nucleoside transport inhibitors that inhibit cellular uptake of adenosine (adenosine uptake inhibitors) and thereby protect cells from the potentially toxic effects of high adenosine concentrations comprise a first class of protective agent. Many adenosine uptake inhibitors have been described in the literature, including dipyridamole, propentofylline, dilazep, nitrobenzylthioinosine, S-(4-nitrobenzyl)-6-thioguanosine, S-(4-nitrobenzyl)-6-thioinosine, iodohydroxy-nitrobenzylthioinosine, and mioflazine. These agents, as well as methods for elucidating additional adenosine uptake inhibitors, are described in Shade, U.S. Pat. No. 5,780,450, incorporated herein by reference. In a preferred embodiment, the nucleoside transport inhibitor is dipyridimole, which is commercially available from Boehringer Ingelheim. Any compound that displays nucleoside transport inhibitor activity at concentrations that are themselves non-toxic to the host are considered appropriate for use in the invention.

[0062] Adenosine kinase catalyzes the phosphorylation of adenosine or deoxyadenosine, and in doing so is postulated to play a central role in the toxicity of adenosine or deoxyadenosine. Therefore, adenosine kinase inhibitors (compounds that inhibit this conversion) comprise a second class of protective agent for inclusion in the unit dose kit of the invention. A few compounds have been reported as potent inhibitors of adenosine kinase with K, 's of less than 100 nM, including 5′-amino-5′-deoxyadenosine [Miller et al., J. Biol. Chem., 254: 2346-2352 (1979)]; 1,12-bis(adenosin-N⁶-yl)dodecane [Prescott et al., Nucleosides & Nucleotides, 8: 297 (1989)]; 5-iodotubercidin [Henderson et al., Cancer Chemotherapy Rep. Part 2, 3: 71-85 (1972); Bontemps et al., Proc. Natl. Acad. Sci. USA, 80: 2829-2833 (1983); Davies et al., Biochem. Pharmacol., 35: 3021-3029 (1986)]; and 5′-deoxy-5-iodotubercidin [Davies et al. (1986)]. Brown et al., U.S. Pat. No. 5,864,033, reports nucleoside analog compounds that are purportedly potent and selective adenosine kinase inhibitors. The Brown patent also describes cell-free and cell-based in vitro assays for screening compounds for adenosine kinase inhibitory activity. Ugarkar et al., U.S. Pat. Nos. 5,795,977 and 5,763,597, report water soluble adenosine kinase inhibitors which are stated to be useful for treatment of cardiovascular and cerebrobvascular diseases, and which are contemplated as useful as a protective agent in this invention. All of the above-cited literature and patent documents are incorporated by reference. Any compound displaying adenosine kinase inhibitory activity at concentrations that display acceptable toxicity profiles are considered appropriate for use in the invention.

[0063] In a related embodiment, the protective agent comprises uridine, cytidine, and/or thymidine or their nucleosides. Such a protective agent is administered at a molar ratio of 1:1 to 1000:1 with the dose of adenosine, and more preferably 10:1 to 100:1.

[0064] In yet another embodiment, the protective agent comprises a compound that inhibits uptake of the ADAI or AMPDAI by cells.

[0065] As a related aspect, the invention provides the use of combinations of compounds or compositions as described above for the manufacture of a medicament for the treatment or neoplastic diseases. In a preferred embodiment, the manufacture of a medicament for the treatment of neoplastic diseases of cells of an epithelial origin are contemplated.

[0066] In a related embodiment, the invention provides methods of using the compositions and unit doses of the invention to kill neoplastic cells in vitro or in vivo. For example, the invention includes a method for inducing cell death in neoplastic cells, comprising: administering a composition according to the invention to a patient having neoplastic cells sensitive to the composition, in an amount sufficient to induce cell death in the neoplastic cells. The invention also includes a method for inducing cell death in neoplastic cells, comprising: administering a unit dose according to the invention to a patient having neoplastic cells sensitive to the compositions which comprise the unit dose, to induce cell death in the neoplastic cells. The administering is repeated as necessary and as tolerated by the patient in order to achieve the anti-neoplastic therapeutic benefit.

[0067] The invention also provides a method of treating a neoplastic disease state in a patient in need of such treatment, comprising the step of: administering to a patient suffering from a neoplastic disease state, a first compound selected from the group consisting of adenosine, adenosine derivatives, and pharmaceutically acceptable salts thereof, and a second compound selected from the group consisting of adenosine deaminase inhibitors (ADAI), adenosine monophosphate deaminase inhibitors (AMPDAI), and pharmaceutically acceptable salts thereof.

[0068] The invention also provides a method of treating a neoplastic disease state in a patient in need of such treatment, comprising the step of: administering to a patient suffering from a neoplastic disease state associated with elevated adenosine levels compared to cells in healthy tissue, a compound selected from the group consisting of adenosine deaminase inhibitors (ADAI), adenosine monophosphate deaminase inhibitors (AMPDAI), and pharmaceutically acceptable salts thereof. This method may further comprise the initial step of: screening a mammalian subject to identify a neoplastic disorder characterized by cells with elevated adenosine levels compared to cells in healthy tissue.

[0069] The invention also provides a method of inducing cell death in tumor cells, comprising administering to a human subject a composition comprising a compound selected from the group consisting of adenosine deaminase inhibitors (ADAI), adenosine monophosphate deaminase inhibitors (AMPDAI), and pharmaceutically acceptable salts thereof, wherein the human subject has a tumor with elevated adenosine in the tumor cells or in extracellular fluid of the tumor, and wherein the composition is administered in an amount sufficient to induce cell death in cells of the tumor.

[0070] Similarly, the invention provides a method of inducing cell death in tumor cells, comprising steps of screening a human subject for elevated adenosine in a tumor or in extracellular fluid of a tumor, and administering to a human subject diagnosed with the tumor with the elevated adenosine a composition comprising a compound selected from the group consisting of adenosine deaminase inhibitors (ADAI), adenosine monophosphate deaminase inhibitors (AMPDAI), and pharmaceutically acceptable salts thereof, wherein the composition is administered in an amount sufficient to induce cell death in cells of the tumor.

[0071] Adenosine levels can be assayed from tissue or fluid of a subject. For example, cells from a tumor biopsy can be lysed and adenosine concentrations assayed by microdialysis (Blay et al., Cancer Res. 57: 2602-2605 (1997) followed by either high performance liquid chromatography (HPLC, Di Pierro et al., Anal. Biochem. 231: 407-412 (1995)) or a real-time enzymatic quantification using a microdialysis biosensor (Dale et al. J. Physiol. 511(1): 265-272 (1998); Ibid 526(1): 143-155 (2000). A combination of microdialysis and real-time enzymatic quantification can also be used to assay adenosine levels in samples of extracellular fluid, lymph, or other fluids. Alternatively, high adenosine levels can be ascertained from microscopic and/or histological examinations of the tumors. As noted previously, tumors that show regions of stress, hypoxia, and/or necrosis would presumably have local adenosine concentrations of at least about 5 mM. The assessment of whether adenosine is normal or elevated is a routine analysis made by comparing the adenosine level in the tumor cells or extracellular fluid with the adenosine level in normal (i.e., healthy, non-neoplastic, non-tumor) cells. Preferably, cells of the same tissue type from which the tumor originated are used as the control (reference/baseline) measurement for normal levels of adenosine. Comparative adenosine levels have been measured in normal and damaged brain (Schrier et al. Biochem. Pharm. 61:417-425 (2001)) and myocardial cells in rodents (Mubagwa et al. Cardiovascular Research 52: 25-39 (2001)), as well as in normal and cancerous lung and colon tissue (Blay et al. Cancer Research 57:2602-2605 (1997)). Thus, adeonosine concentrations in healthy ovarian tissue can be compared with adenosine concentrations in ovarian cancer. Single agent deaminase inhibitor therapy of tumors with elevated adenosine is preferred because the elevated adenosine makes the tumors more susceptible to the effects of the deaminase than healthy cells of the patient that have normal adenosine concentrations.

[0072] Although methods of the invention may be used to treat any neoplastic disease state, it is specifically contemplated that the methods be used to treat neoplastic diseases of cells, tissues, or organs of epithelial origin. Such epithelial malignancies include malignancies of the lungs, breasts, gastrointestinal system, genitourinary tract, or reproductive organs, many of which are considered refractory to many existing cancer therapies. In a highly preferred embodiment, the invention provides improved methods of treating ovarian cancer.

[0073] As explained above, the compounds are preferably formulated as compositions with one or more pharmaceutically acceptable carriers. They may be administered serially or simultaneously, and may be administered as part of a single formulation or as two separate formulations. Irrespective, a therapeutically effective amount of the compounds is administered to the patient. A therapeutically effective dose refers to that amount of the compounds that results in a reduction in the rate of growth of the undesired neoplastic cells, or more preferably a killing of the neoplastic cells resulting in their reduction or elimination to prolong the survival of the patient. The therapeutically effective dose also is a dose with acceptable levels of toxicity. In many cases a considerable level of toxicity or side effects is considered acceptable due to the lethality of the neoplastic disease state if left untreated.

[0074] Toxicity and therapeutic efficacy of such compounds can be determined by standard pharmaceutical procedures using, e.g., cell cultures and/or experimental animals. For example, one determines the LD₅₀ (the dose lethal to 50% of the population) and the ED₅₀ (the dose therapeutically effective in 50% of the population) in an accepted laboratory animal model to provide guidance for human dosing. The dose ratio between toxic and therapeutic effects is the therapeutic index and it can be expressed as the ratio LD₅₀/ED₅₀. Combinations of compounds which exhibit large therapeutic indices (preferably greater 2; more preferably greater than 10 or greater than 50) are preferred. The dosage required to achieve the desired concentration of therapeutic agents in the environment of a tumor will vary depending upon the dosage form employed and the route of administration utilized.

[0075] Cell culture assays and in vivo animal model studies, such as those described herein, permit initial estimates of therapeutically effective doses. Monitoring concentrations of the therapeutic compounds in the plasma, and/or in the tumor environment provide additional guidance.

[0076] The effective anti-cancer amount of the compounds are administered to patients in a manner that inhibits or prevents tumor growth and/or metastasis. In view of the teachings herein, the attending physician will be able to vary the amount of the compounds, the carrier, the dosing frequency, and the like, taking into consideration such factors as the particular neoplastic disease state and its severity; the overall condition of the patient; the patient's age, sex, and weight; the mode of administration; the suitability of concurrently administering systemic anti-toxicity agents; monitoring of the patient's vital organ functions; and other factors typically monitored during cancer chemotherapy.

[0077] Although an appropriate formulation, route of administration, dose, and dosing schedule, and duration of treatment can be optimized by a patient's physician according to the teachings herein, in preferred embodiments it is contemplated that the pharmaceutical formulations are administered to obtain concentrations of the compound or compounds in the region of the tumor of about 0.01 to 1000 μM, and preferably about 0.5 to 500 μM, more preferably about 1 to 100 μM, and more preferably about 10 to 50 μM or about 20 μM. In a preferred embodiment, the molar ratio of the two compounds in the region of the tumor is 0.01 to 100; in a highly preferred embodiment 0.1 to 10; and in a very highly preferred embodiment, about 1.0.

[0078] When treating tumors having elevated adenosine with a deaminase inhibitor alone, the physician also can optimize dose, dosing, and duration according to the teachings herein. Although a particular deaminase inhibitors enzymatic efficacy is not altered by the presence or absence of adenosine, screening the tumor for adenosine concentration facilitates dosing because higher adenosine in the tumor is expected to be correlated with increased anti-tumor efficacy of the deaminase inhibitor. In preferred embodiments it is contemplated that the pharmaceutical formulations are administered to obtain concentrations of the compound or compounds in the region of the tumor of about 0.01 to 1000 μM, and preferably about 0.5 to 500 μM, more preferably about 1 to 100 μM, and more preferably about 10 to about 20 μM. In a preferred embodiment, the molar ratio of the ADAI and/or AMPDAI to adenosine in the region of the tumor is 0.01 to 100; in a highly preferred embodiment 0.1 to 10; and in a very highly preferred embodiment, about 1.0. Concentrations of the compound or compounds in these ranges are effective to inhibit adenosine deaminases for at least about 12 to about 96 hours. The inhibition of ADA in vivo can be determined by measuring ADA from red blood cell samples (Sims et al. J. Biol. Chem. 274: 25701-7 (1999); J. Spychala Biochem. Biophys. Res. Commun., 148: 106-11 (1987)).

[0079] As explained above, certain agents such as homocysteine compounds are expected to enhance the anti-tumor efficacy of the adenosine/enzyme inhibitor single agent or combination therapy of the invention. Methods of treatment that include administration of homocysteine compounds or other additional compounds to a patient, in amounts effective to increase the anti-neoplastic activity of the first and second compounds, are specifically contemplated.

[0080] The therapeutic compounds may be administered by any route of drug administration, depending on the site of the cancer to be attacked. These include parenteral, intravenous, intracavitary, intrathecal, interstitial, intravesicular, intraperitoneal, topical, transdermal, transmucosal, and the like. Repeated injections or continuous infusions of the drug combination lasting for hours or days is contemplated, as toxicity permits, until the desired therapeutic results have been achieved. Continuous regional or system infusions by drug delivery pump is specifically contemplated.

[0081] In a highly preferred embodiment for treating many patients, especially patients wherein a cancer has not metastised, a route of administration is selected to maximize the concentration of the therapeutic agents in the region of the tumor while minimizing the systemic concentration, e.g., in the peripheral blood or plasma. For example, to treat a cancer localized to the peritoneal cavity, such as ovarian cancer, at least one of the first and second therapeutic compounds (and preferably both) is infused into the peritoneal cavity, e.g., with a catheter and/or a drug delivery pump, to effect a higher concentration of the agent in the peritoneal cavity than in the peripheral blood. The infusion is continued or repeated as necessary to maintain a desired therapeutic concentration of the chemotherapeutic compounds in the peritoneal cavity for, e.g., 12 to 24 hours.

[0082] In a related aspect, the invention provides for co-treatment of the patient with a protective agent, such as a nucleoside transport inhibitor or adenosine kinase inhibitor as described above, in an amount effective to reduce systemic toxic side-effects of the anti-neoplastic compounds. For example, a patient that is being given intraperitoneal injections or infusions for treatment of a localized tumor in the peritoneal cavity is simultaneously administered a pharmaceutical preparation of a protective agent intravascularly. The dosing of the protective agent is selected to achieve a systemic concentration that is high enough to prevent at least some of the toxic side effects of the anti-neoplastic agents, but is low enough so as not to significantly diminish the anti-neoplastic effects of the compounds on the tumor itself. This balance is achievable by using routes of administration that induce higher concentrations of the anti-neoplastic agents in and around the tumor than in the patient as a whole, or in organs or fluids containing lymphoid cells particularly susceptible to toxic side effects. For example, the anti-neoplastic agents are administered locally to the tumor, to achieve high local concentrations thereof, while the protective agent is systemically administered at concentrations that are protective against the lower systemic concentrations of the anti-neoplastic agents, but not against the higher concentrations localized around the tumor. Alternatively, the protective agent itself is administered locally, to protect one or more healthy organs that would otherwise be particularly susceptible to the toxic side-effects of the neoplastic compounds. This concentration differential is maintained by periodically or continuously monitoring concentrations of the agents in the patient, and/or by knowledge of the pharmacokinetics of the different agents.

[0083] The invention is further described by reference to the following examples, which are intended as illustrative only and not as limiting the invention.

EXAMPLE 1 Anti-Tumor Efficacy of Adenosine and Coformycin Combination Against Cultured Epithelial Cancer Cell Lines

[0084] The following experimental protocols demonstrate that adenosine in combination with a deaminase inhibitor, namely coformycin, is an effective combination chemotherapy for killing two different cancer cell lines representing tumors of epithelial origin, namely breast and ovarian tumors.

[0085] For the experiments MCF7 breast cancer cells and OVCAR3 ovarian cancer cells (both obtained from the American Type Culture Collection (ATCC), Manassas, Va.) were cultured in RPMI 1640 media containing 10% fetal calf serum (Life Technologies, Gaithersburg, Md.). After 24 hours of culturing at 37° C. in 5% CO₂, additional medium was added containing either adenosine (final concentration 10 μM), coformycin (final concentration 10 μM), or 10 μM each of adenosine and coformycin. Additional media alone was added to control cultures.

[0086] The cells were cultured in these chemotherapeutic media for an additional 60 hours, at which time the viability of the cells were determined using an MTT assay (Celltitre 98 Aqueous 1, Promega, Madison, Wis.). FIG. 1 depicts the results of this assay, where cell viability as a percentage of control is depicted, with error bars to indicate standard deviation (representative of three different analyses). As can be seen in the figure, neither chemotherapeutic agent was effective alone at arresting cell growth, with cell viability measuring in excess of 100% of the controls. However, the combination chemotherapy was toxic to both tumor cell lines.

EXAMPLE 2 Anti-Tumor Efficacy of Adenosine and Coformycin Combination Against Additional Cultured Epithelial Cancer Cell Lines

[0087] The procedures described in Example 1 were repeated to test the anti-tumor efficacy of the adenosine/coformycin combination against several additional cell lines obtained from the ATCC: MCF7 and MDA MB 231 breast cancer cell lines; OVCAR 3 and OVCAR 5 ovarian cancer cell lines; HT 29 colon cancer cell line; and PC3, TSU-Pr1, and DU14 prostatic cancer cell lines. FIG. 2 depicts the results of this assay, where cell viability as a percentage of control is depicted, with error bars to indicate standard deviation (representative of three different analyses). As can be seen in the figure, the combination of 10 μM adenosine and 10 μM coformycin reduced survival of all tested tumor cell lines by at least 50%, and was highly effective against the prostatic and ovarian cancer cell lines.

EXAMPLE 3 Identification of Anti-Toxicity Agentsto Improve Safety and Prevent Systemic Toxicity

[0088] In a preferred embodiment, patients that are treated with the chemotherapeutic combination of the invention to destroy localized tumors are additionally treated systemically with a drug designed to block the cellular uptake of at least one of the chemotherapeutic agents. As demonstrated in Example 1, blocking one agent is sufficient to reduce or eliminate toxicity. Systemic administration of a protective agent will prevent toxicity to non-cancerous tissues and also permit local administration of higher chemotherapeutic doses at the site of tumors.

[0089] Assays were performed to determine whether the nucleoside transport inhibitor dipyridamole or the adenosine kinase inhibitor 5′-amino-5′-deoxyadenosine were capable of protecting sensitive cell lines from the combination Ado/CF chemotherapy. The OVCAR3 ovarian cancer cell line was cultured as described in Example 1 for 24 hours and then treated with either 5 μM (final concentration) dipyridimole alone; 10 μM adenosine plus 10 μM coformycin alone; or the combination of these two treatments. In a control sample, culture media alone was added. The cultures were grown for an additional 60 hours and then analyzed for cell growth. The results of the assay are depicted in FIG. 3, where cell viability as a percentage of the control is depicted, with error bars to indicate standard deviation (representative of three different analyses). As shown therein, treatment with dipyridamole alone permitted cell growth comparable to the control, whereas the Ado/CF combination therapy reduced cell growth to less than 10% of the control. When dipyridamole was added in combination with the toxic levels of Ado/CF, the cancer cells again were able to grow at levels approximating that of the untreated control.

[0090] The same experiments were repeating using 5 μM (final concentration) 5′-amino-5′-deoxyadenosine alone; 5 μM adenosine plus 10 μM coformycin alone; or the combination of these two treatments. As depicted in FIG. 4, the 5′-amino-5′-deoxyadenosine was mildly toxic to the cancer cells when administered alone (cell growth ˜80% of control), but was able to essentially completely block the severe toxic effects of the Ado/CF combination treatment.

[0091] The dipyridimole experiment was repeated using several different tumor cell lines obtained from the ATCC: OVCAR3, OVCAR5, DU145, PC3, LNCaP, TSU-PR1, and MCF-7. As depicted in FIG. 5, the dipyridamole treatment consistently was able to protect the otherwise-sensitive tumor cell lines from the cytotoxic effects of Ado/CF treatment.

[0092] The foregoing data provides evidence that a nucleoside transport inhibitor and/or an adenosine kinase inhibitor are capable of protecting cells against the toxic effects of adenosine/coformycin combination therapy, and thus indicate a therapeutic use for such agents to protect healthy tissues during localized cancer chemotherapy.

EXAMPLE 4 Coformycin is More Potent Than Deoxycoformycin When Used with Adenosine in Tumor Cell Toxicity Assays

[0093] Existing literature recognizes both coformycin (CF) and deoxycoformycin (dCF) as inhibitors of adenosine deaminase (ADA) and AMP deaminase (AMPDA) enzymes. Whereas dCF is recognized as a more potent inhibitor of ADA than CFby 2.5-fold [K₁=0.01 nM versus 0.025 nM, see Cha S., et al., Biochem. Pharmacol. 24: 2187-2197 (1975), and Agarwal, R P. et al., Biochem. Pharmacol. 26: 359-367 (1977)], CF is a 50-fold more potent inhibitor of AMPDA. The following experiments were conducted to compare the anti-tumor efficacy of adenosine in combination with each of these deaminase inhibitors against a tumor cell line of epithelial origin.

[0094] The procedures described in Example 1 were repeated using cell lines OVCAR 3, OVCAR 5, MCF7, and HT 29 and using 5 μM adenosine in combination with either 5 μM CF or 5 μM dCF as the therapeutic combination of agents. FIG. 6 depicts the results of this assay, where cell viability as a percentage of control is depicted. As can be seen in the figure, the coformycin consistently potentiated to toxicity of the adenosine to a greater extent than the deoxycoformycin, and the differences were especially striking against the ovarian cancer cell lines OVCAR3 and OVCAR5.

[0095] Without intending to be limited to any particular theory, the foregoing data suggests that the combination chemotherapy of the invention acts through a mechanism involving inhibition of AMPDA or inhibition of both AMPDA and ADA. Based on these data, AMPDA inhibitors are postulated to comprise a preferred class of compounds for use in the invention, in combination with adenosine. A combination of ADA and AMPDA inhibitors, either embodied in a single compound such as CF or as a combination of an ADA inhibitor compound and an AMPDA inhibitor compound, are also a preferred class of compounds for use with adenosine in the invention. Repetition of the foregoing experiments with compounds that selectively inhibit ADA or selectively inhibit AMPDA, alone or in combination, will identify the most effective type of inhibitor or inhibitor combination for each particular tumor type.

EXAMPLE 5 Adenosine is More Potent Than Select Adenosine Derivativeswhen Used with an ADAI/AMPDAI in Tumor Cell Toxicity Assays

[0096] The following experiments were performed to compare the cytotoxicity ofadenosine and selected adenosine derivatives when used in combination with an ADAI or AMPDI compound.

[0097] The procedures described in Example 1 were repeated using the OVCAR 3 ovarian cancer cell line, and using as therapeutic agents 10 μM coformycin in combination with 10 μM of either adenosine, 2-chloroadenosine, 8-chloroadenosine, or 8-chloro-cAMP. Cell viability data, determined as described above, is presented in the following table. Viability (Percent Compound of Control) Adenosine (10 μM) and Coformycin (10 μM)   3 ± 0.2 2-chloroadenosine (10 μM) and Coformycin (10 μM) 111 ± 5  8-chloroadenosine (10 μM) and Coformycin (10 μM) 94 ± 6  8-chloro-cAMP (10 μM) and Coformycin (10 μM) 98 ± 3 

[0098] As can be seen from the table, the adenosine was a much more potent cytotoxic agent when used in combination with CF than any of the adenosine derivatives tested.

[0099] The foregoing results demonstrate that the use of adenosine in therapeutic combinations of the invention confers greater antineoplastic activity against at least certain cell types than a number of adenosine derivatives. In addition, use of adenosine provides the additional advantage that its toxic side-effects can be modulated using certain anti-toxicity agents, as described above. Dipyridamole has shown to be ineffective for blocking the toxic effects of cordycepin when substituted for adenosine in experiments such as those described in Example 3.

EXAMPLE 6 In vivo Anti-Tumor Efficacy

[0100] Female nude mice (Harlan Labs) that are seven weeks old are weight matched and randomly divided into several groups. The animals are maintained on standard laboratory diets and drinking water. All animals are injected abdominally with anywhere from approximately 2 cells to 1 million cells from a human or murine ovarian cancer cell line.

[0101] Beginning one day after tumor injection, the different groups of mice are each treated with a pharmaceutical composition comprising either adenosine alone, coformycin alone, adenosine plus coformycin at varying concentrations, or comprising the pharmaceutical carrier alone (control). For some groups, the pharmaceutical composition further includes homocysteine thiolactone. In one variation, intraperitoneal injections of the are performed at regular weekly intervals for eight weeks. In a preferred variation, after the initial injection into the peritoneal cavity, a drug delivery pump is used to continuously deliver selected amounts of the pharmaceutical compositions to the animals for, e.g., 12, 18, 24, 36, or 48 hours. Blood may be drawn from the ear or tails of animals to determine drug concentrations.

[0102] After 21-35 days of treatment, the animals are studied to determine treatment efficacy. Animal weight and duration of animal survival; measurements of tumor weight (following animal sacrifice), and/or other conventional factors are analyzed. Improved survival times and/or decreased tumor burden in the combination therapy groups compared to the control group and/or to the groups receiving single agents is considered indicative of therapeutic efficacy.

[0103] The experiment is repeated using alternative tumor cell lines; and/or using adenosine derivatives; and/or using alternative deaminase inhibitors to demonstrate therapeutic efficacy in other variations of the invention. The experiment is further repeated in alternative animal models, including models known to spontaneously develop various epithelial cancers and in larger mammals such as dogs, pigs, or primates, that more closely approximate humans.

EXAMPLE 7 Use of Anti-Toxicity Agents in vivo to Improve Safety and Prevent Systemic Toxicity

[0104] Procedures described in Example 6 are repeated with the following variation. In addition to localized infusion of therapeutic agents into the peritoneal cavity, some animals are also injected intravenously, intraarterially, or intramuscularly with a pharmaceutical composition comprising selected concentrations of a protective agent such as a nucleoside uptake inhibitor or an adenosine deaminase inhibitor. Some animals receiving the protective agent are administered dosages of the therapeutic agents that are equivalent to or greater than the maximum doses tolerated in the studies wherein no protective agents were employed.

[0105] After 21-35 days of treatment, the animals are studied to determine treatment efficacy. Animal weight and duration of animal survival; measurements of tumor weight (following animal sacrifice), and/or other conventional factors are analyzed. Improved survival times and/or decreased tumor burden in the combination therapy groups that receive the protective agent, compared to groups that do not, is considered indicative of therapeutic efficacy. Therapeutic efficacy also is demonstrated by equivalent survival time combined with observed decreases in toxic side effects (e.g., fever, chills, diarrhea, loss of weight or appetite, etc.) in the animals that receive the protective agent.

EXAMPLE 8 In vivo Anti-Tumor Efficacy for Coformycin Alone

[0106] Seven week old, female nude mice (Harlan Labs) were weight matched and randomly divided into several groups. The animals were maintained on standard laboratory diets and drinking water. All animals were injected intra-peritoneally with anywhere from approximately 1 million cells to 10 million cells from either OVCAR3 or OVCAR5 human ovarian cancer cell lines. When the tumors were in excess of 1 cm³, they were removed from the animals and cut into smaller sizes of 20 mg each. The tumors were then incubated in culture medium without drugs (untreated) or with a) 10 μM adenosine and 10 μM of coformycin, b) 10 μM adenosine and 20 μM of coformycin, c) 10 μM of coformycin alone, or d) 20 μM of coformycin alone. Each incubation was for 96 hours. A cell proliferation assay was then performed using a CellTiter 96 Aqueous One Solution Cell Proliferation Assay (Promega) with [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulphophenyl)-2H-tetrazolium inner salt (MTS) reagent. The percent of viable cells was determined relative to the untreated tumor module. The experiments were repeated three independent times. As shown in FIG. 7, 20 μM coformycin was as effective at reducing viability of the tumors derived from both cells lines as the combination of 10 μM adenosine with 10 μM coformycin. These results contrast sharply with data observed from Example 1, which involved the same tumor cell lines grown in culture, and which indicated that the levels of coformycin tested alone were ineffective at killing the same cancer cells. Without intending to be limited to a particular theory of the invention, tumors in vivo are hypothesized to contain elevated adenosine (relative to healthy tissue), resulting perhaps from a hypoxic environment, making the tumors sensitive to the ADAI or AMPDAI as a single agent.

[0107] While the present invention has been described in terms of specific embodiments, it is understood that variations and modifications will occur to those in the art, all of which are intended as aspects of the present invention. Accordingly, only such limitations as appear in the claims should be placed on the invention. 

What is claimed is:
 1. A method of inducing cell death in tumor cells, comprising administering to a human subject a composition comprising a compound selected from the group consisting of adenosine deaminase inhibitors (ADAI), adenosine monophosphate deaminase inhibitors (AMPDAI), and pharmaceutically acceptable salts thereof, wherein the human subject has a tumor with elevated adenosine in the tumor cells or in extracellular fluid of the tumor, and wherein the composition is administered in an amount sufficient to induce cell death in cells of the tumor.
 2. A method of inducing cell death in tumor cells, comprising: screening a human subject for elevated adenosine in a tumor or in extracellular fluid of a tumor, and administering to a human subject diagnosed with the tumor with the elevated adenosine a composition comprising a compound selected from the group consisting of adenosine deaminase inhibitors (ADAI), adenosine monophosphate deaminase inhibitors (AMPDAI), and pharmaceutically acceptable salts thereof, wherein the composition is administered in an amount sufficient to induce cell death in cells of the tumor.
 3. A method according to claim 1 or 2 wherein the composition further comprises a pharmaceutically acceptable carrier.
 4. A method according to claim 1 or 2, further comprising administering to the subject homocysteine in an amount effective to potentiate the inducing cell death by said composition.
 5. A method according to claim 1 or 2 wherein the compound has both ADAI and AMPDAI activity.
 6. A method according to claim 1 or 2 wherein the compound is deoxycoformycin (dCF).
 7. A method according to claim 1 or 2 wherein the compound is coformycin (CF).
 8. A method according to claim 1 or 2 wherein the neoplastic disease state is an epithelial malignancy.
 9. A method according to claim 1 or 2 wherein the tumor is selected from malignancies of the lungs, breasts, gastrointestinal system, genitourinary tract, or reproductive organs.
 10. A method according to claim 1 or 2 wherein the tumor is ovarian.
 11. A method according to claim 1 or 2 wherein the composition is administered in a unit dose to effect a higher concentration of the composition in or around said tumor than in the peripheral blood.
 12. A method according to claim 11 wherein the tumor is situated in the peritoneal cavity, and wherein the administering step comprises infusing or injecting the composition into the peritoneal cavity.
 13. A method according to claim 12 wherein the infusing is performed through a catheter inserted into the peritoneal cavity.
 14. A method according to claim 13 wherein the unit dose is administered at concentrations effective to maintain a peritoneal concentration of the compound of at least 5 μM for at least 12 hours.
 15. A method according to claim 13 wherein the unit dose is administered at concentrations effective to maintain a peritoneal concentration of the compounds of about 5 μM -20 μM for at least 12 hours.
 16. A method according to claim 13 wherein the unit dose is administered at concentrations effective to inhibit adenosine deaminases for at least about 12 to about 96 hours.
 17. A method according to claim 11, further comprising the step of systemically administering to said patient a composition comprising a protective agent selected from the group consisting of a nucleoside transport inhibitor, an adenosine kinase inhibitor, combination thereof, and pharmaceutically acceptable salts thereof, in an amount effective to reduce systemic side effects of said compound.
 18. A method according to claim 2 wherein the composition is administered in a unit dose to effect a higher concentration of the composition in or around said tumor than in the peripheral blood.
 19. A method according to claim 18 wherein the tumor is situated in the peritoneal cavity, and wherein the administering step comprises infusing or injecting the composition into the peritoneal cavity.
 20. A method according to claim 19 wherein the infusing is performed through a catheter inserted into the peritoneal cavity.
 21. A method according to claim 20 wherein the unit dose is administered at concentrations effective to maintain a peritoneal concentration of the compound of at least 5 μM for at least 12 hours.
 22. A method according to claim 20 wherein the unit dose is administered at concentrations effective to maintain a peritoneal concentration of the compounds of about 5 μM -20 μM for at least 12 hours.
 23. A method according to claim 20 wherein the unit dose is administered at concentrations effective to inhibit adenosine deaminases for at least about 12 to about 96 hours.
 24. A method according to claim 18, further comprising the step of systemically administering to said patient a composition comprising a protective agent selected from the group consisting of a nucleoside transport inhibitor, an adenosine kinase inhibitor, combination thereof, and pharmaceutically acceptable salts thereof, in an amount effective to reduce systemic side effects of said compound.
 25. A kit for treating a neoplastic disease state comprising a container holding a compound selected from the group consisting of adenosine deaminase inhibitors (ADAI), adenosine monophosphate deaminase inhibitors (AMPDAI), combinations thereof, and pharmaceutically acceptable salts thereof and a label attached to or packaged with the container, the label describing use of the compound for inducing cell death in tumors with elevated adenosine. 